There currently exists a number of applications based on technologies that are implemented in various enterprise and carrier environments. These relevant technologies include transport-layer IP VPNs, Voice VPNs with E.164 numbering, and Enterprise VoIP networks.
A transport-layer IP VPN enables a network administration to use a shared network to offer a customer service that emulates the characteristics of a private network (such as performance, reliability, security and QoS) for the customer. An example of where a VPN has seen application is in areas where a person is working remotely from his or her office. The person can connect to a VPN over a public network, such as the Internet, and be connected with the office intranet, and thus have access to networked drives or printers as if the person were in the office. State-of-the-art technologies that are used to implement IP VPNs include MPLS, and IP tunneling protocols such as L2TP.
Voice VPNs with E.164 numbering implemented in a Public Switched Telephone Network (PSTN) typically provide customers with special customer-specific capabilities such as private numbering plan and various enhanced features such as follow me, call forwarding, etc. Other voice VPNs that are implemented using SINA (Static Integrated Network Arrangement) arrangements or private lines typically have features that are limited to capabilities supported by the customers' connected PBXs.
An enterprise VoIP network typically deploys pairs of LADs (Integrated Access Devices) in customer sites to integrate voice and data using technologies ranging from TDM (Time Division Multiplexing) to packetization technologies such as AAL2 (ATM Adaptation Layer 2).
Many of these technologies have been successfully utilized in the implementation of small-scale enterprise networks. However, the application of most of these technologies in a carrier environment to provide comprehensive voice and integrated voice and data services is still very much lacking.
It would, therefore, be desirable to provide an architecture that allows a carrier to provide full capability voice VPN services to multiple customers over a common shared packet network.